The present invention relates to phonograph turntables and in particular to an improved turntable designed for use in the playback of phonograph record matrices and stampers.
During the process of manufacturing phonograph records an important step comprises the formation of a metallic stamper from which the final records are mass produced. The stamper must comprise an exact negative of the record grooves since any imperfection in the stamper will reproduce in the records. The stamper is made from a record "mother" which in turn is obtained through a series of manufacturing procedures from a matrix and in turn a master cut at a recording or "mixdown" session. The stamper is a flat sheet steel member having a nickel plating on its information bearing surface.
Heretofore, it has not been possible to test the accuracy of the information on the stamper directly. To test a stamper an actual record had to be formed from that stamper and then played back on conventional equipment. Any imperfection in the stamper would reflect itself in an imperfection in the sample record. The precise location of the problem on the record sample had to be located and its counterpart on the stamper then had to be found. In many cases the problem on the stamper could be cured by suitably polishing the stamper. After this was done, the stamper then had to be used to produce another sample record which then tested as before and the procedure repeated until perfect records were produced.
It can thus be seen that considerable time and effort could be saved by providing means to enable the direct playback of a phonograph stamper.
In view of the above, it is the principal object of the present invention to provide a phonograph record stamper playback turntable which enables direct playback of the information encoded on the stamper.
A further object is to provide such a turntable which enables playback with a high degree of fidelity and on which corrections in the stamper may be made.